Re: introduce dynamic shared memory registry

From: Nathan Bossart <nathandbossart(at)gmail(dot)com>
To: Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>
Cc: Abhijit Menon-Sen <ams(at)toroid(dot)org>, Michael Paquier <michael(at)paquier(dot)xyz>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: introduce dynamic shared memory registry
Date: 2024-01-16 16:07:48
Message-ID: 20240116160748.GB100542@nathanxps13
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On Tue, Jan 16, 2024 at 10:28:29AM +0530, Bharath Rupireddy wrote:
> I think it's better for GetNamedDSMSegment() to error out on empty
> 'name' and size 0. This makes the user-facing function
> GetNamedDSMSegment more concrete.

Agreed, thanks for the suggestion.

> +void *
> +GetNamedDSMSegment(const char *name, size_t size,
> + void (*init_callback) (void *ptr), bool *found)
> + Assert(found);
> Why is input parameter 'found' necessary to be passed by the caller?
> Neither the test module added, nor the pg_prewarm is using the found
> variable. The function will anyway create the DSM segment if one with
> the given name isn't found. IMO, found is an optional parameter for
> the caller. So, the assert(found) isn't necessary.

The autoprewarm change (0003) does use this variable. I considered making
it optional (i.e., you could pass in NULL if you didn't want it), but I
didn't feel like the extra code in GetNamedDSMSegment() to allow this was
worth it so that callers could avoid creating a single bool.

Nathan Bossart
Amazon Web Services:

Attachment Content-Type Size
v8-0001-reorganize-shared-memory-and-lwlocks-documentatio.patch text/x-diff 9.3 KB
v8-0002-add-dsm-registry.patch text/x-diff 22.6 KB
v8-0003-use-dsm-registry-for-pg_prewarm.patch text/x-diff 3.1 KB

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